1. Field of the Invention
The present invention relates to an apparatus for measuring the thermal properties of and making thermomechanical modifications an the surface of a particular material using a Peltier tip, which works as a heat source and as a temperature sensor simultaneously.
2. Description of the Related Art
In a semiconductor integrated circuit, heat generated per unit area increases as the integration density increases. To prevent occurrences of a short or a malfunction due to high temperature in an integrated circuit, the measurements of thermal properties of a semiconductor device are essential. The investigations of homogeneity of composite materials and the grain size of each individual material are important in the fields of medical science, material science, and chemical engineering, and so on. Also, in studying thin films or multilayer films, the precise measurements of thermal properties such as thermal conductivity and specific heat, which are fundamental physical quantities involving transport phenomena and internal degrees of freedom of a system, are required. Furthermore, the development of high density recording media is actively in progress through thermomechanical modifications of polymers and glassy films using a scanning thermal microscope.
As described above, the characterizations of thermal properties in the fields of semiconductors composites, and thin films are very important for engineering and scientific purposes. However, in an actual measurement, it is difficult to conduct quantitative analysis since the mass of a material is extremely small and the measurement apparatus has low spatial resolution.
Conventionally, a method of measuring thermal properties on a material surface includes the use of a Peltier tip made of a thin resistive wire as a heat source by applying a current to the tip, while measuring temperature through the change in resistance, thereby grasping thermal properties qualitatively. However, this method suffers from sensitivity limitations since the exchange of heat, generated over the entire tip by Joule heating, occurs only at a point that is in contact with a material. In addition, if the conventional method is applied to make thermomechanical modifications, there are limitations in spatial resolution and speed, since only heating is possible at the tip.
To solve the above problems, it is an object of the present invention to provide an apparatus for measuring thermal properties of and making thermomechanical modifications on a material surface using a Peltier tip. The Peltier tip is defined as a junction of different metallic wires, which is distinguished from a conventional thermocouple by the fact that it works as a point heat source and a point temperature sensor simultaneously when an electric current flows into the tip. This novel functionality of the Peltier tip offers the way to the thermal characterizations of a material surface with submicron-scale spatial resolution, and high sensitivity, while providing high spatial resolution and speed for thermal modifications since both heating and cooling are possible at the Peltier tip. The apparatus includes: a signal generator that drives an electric current into the Peltier tip; an ammeter connected to the signal generator for measuring current; a bridge circuit consisting of junctions of metallic wires, which is connected to the ammeter, wherein one junction of the metallic wires is made in the form of the Peltier tip; and a lock-in amplifier connected to both symmetrical terminals of the bridge circuit for amplifying and detecting voltages due to temperature oscillation detected by the Peltier tip.